Comparative studies of chloride and chloride/citrate based electrolytes for zinc–polyaniline batteries

Abstract

Electrochemical behavior of zinc and thin polyaniline (PANI) polymerized from 0.1 M HCl to 0.1 M aniline on graphite electrode, in 0.2 M ZnCl2 and 0.50 M NH4Cl (chloride electrolyte) and with addition of 0.33 M Na-citrate (chloride/citrate electrolyte) were investigated. In the chloride/citrate comparing with chloride containing electrolyte zinc electrode shows negative shift of the open circuit potential of ∼130 mV, decreases of exchange current density for more than order of magnitude and increase of cathodic Tafel slope, due to the zinc ions complexation. In citrate/chloride electrolyte zinc dendrite formation were suppressed. In the range of investigated charge/discharge current densities of 0.25–1 mA cm−2, initially obtained specific capacity was in the range of 140–85 mAh g−1, respectively. In cycling regime specific capacity and columbic efficiency were affected with anodic potential limits. For anodic potential limits of 0.32 V (SCE) citrate/chloride electrolyte shows better characteristic than chloride electrolyte, due to the influence of citrate ions on negative shift of doping reaction. Increasing anodic potential limit to 0.5 V (SCE), leads to faster decrease of specific capacity in citrate/chloride than in chloride electrolyte, which was. explained by higher hydrophilic effect of citrate anions.